Fix reading of diff tool configuration in .gitconfig (close #32)

Author: laurentkempe

GitDiffMargin/Git/GitCommands.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Runtime.InteropServices;
 using EnvDTE;
 using LibGit2Sharp;
 using Microsoft.VisualStudio.Text;
@@ -15,7 +16,7 @@ public class GitCommands : IGitCommands
 
         public GitCommands(IServiceProvider serviceProvider)
         {
-            _dte = (DTE) serviceProvider.GetService(typeof (_DTE));
+            _dte = (DTE)serviceProvider.GetService(typeof(_DTE));
         }
 
         private const int ContextLines = 0;
@@ -98,26 +99,31 @@ public void StartExternalDiff(ITextDocument textDocument)
 
             using (var repo = new Repository(discoveredPath))
             {
-                var diffGuiTool = repo.Config.Get<string>("diff.guitool");
+                var diffGuiTool = repo.Config.Get<string>("diff.tool");
 
                 if (diffGuiTool == null) return;
 
-                var diffCmd = repo.Config.Get<string>("difftool." + diffGuiTool.Value + ".path");
-
                 var indexEntry = repo.Index[filename.Replace(repo.Info.WorkingDirectory, "")];
                 var blob = repo.Lookup<Blob>(indexEntry.Id);
 
                 var tempFileName = Path.GetTempFileName();
                 File.WriteAllText(tempFileName, blob.GetContentText());
-                    
+
+                var diffCmd = repo.Config.Get<string>("difftool." + diffGuiTool.Value + ".cmd");
+                var cmd = diffCmd.Value.Replace("$LOCAL", tempFileName).Replace("$REMOTE", filename);
+
+                string exe;
+                var args = CommandLineToArgs(cmd, out exe);
+
                 var process = new Process
                 {
                     StartInfo =
                     {
-                        FileName = diffCmd.Value,
-                        Arguments = String.Format("{0} {1}", tempFileName, filename)
+                        FileName = exe,
+                        Arguments = string.Join(" ", args)
                     }
                 };
+
                 process.Start();
             }
         }
@@ -141,5 +147,37 @@ public string GetGitRepository(string filePath)
             var directoryInfo = Directory.GetParent(fullPath).Parent;
             return directoryInfo != null ? directoryInfo.FullName : null;
         }
+
+        [DllImport("shell32.dll", SetLastError = true)]
+        static extern IntPtr CommandLineToArgvW(
+
+        [MarshalAs(UnmanagedType.LPWStr)] string lpCmdLine, out int pNumArgs);
+        private static string[] CommandLineToArgs(string commandLine, out string executableName)
+        {
+            int argCount;
+            var result = CommandLineToArgvW(commandLine, out argCount);
+            if (result == IntPtr.Zero)
+            {
+                throw new System.ComponentModel.Win32Exception();
+            }
+
+            try
+            {
+                var pStr = Marshal.ReadIntPtr(result, 0 * IntPtr.Size);
+                executableName = Marshal.PtrToStringUni(pStr);
+                var args = new string[argCount - 1];
+                for (var i = 0; i < args.Length; i++)
+                {
+                    pStr = Marshal.ReadIntPtr(result, (i + 1) * IntPtr.Size);
+                    var arg = Marshal.PtrToStringUni(pStr);
+                    args[i] = arg;
+                }
+                return args;
+            }
+            finally
+            {
+                Marshal.FreeHGlobal(result);
+            }
+        }
     }
 }